In vitro shoot and root organogenesis, plant regeneration and production of tropane alkaloids in some species of Schizanthus

Abstract

A rapid in vitro propagation system leading to formation of shoots from callus, roots, and plantlets was developed for Schizanthus hookeri Gill. (Solanaceae), an endemic Chilean plant. The genus Schizanthus is of particular interest due to the presence of several tropane alkaloids. So far, in vitro propagation of species of this genus has not been reported. Propagation of S. hookeri consisted of two phases, the first one for callus initiation and shoot formation and the second for rhizogenesis and plantlet regeneration. From a single callus that rapidly increased in cell biomass (from similar to 50 mg to similar to 460 mg/culture tube [25 x 130 mm] in 60 days) in the presence of 2.69 mu M NAA and 2.22 mu M BA, more than 10 shoots/callus explant were formed. From the latter, approx. twenty plantlets formed after 90-110 days shoot subculture in medium devoid of growth regulators that favored root formation. Ten alkaloids ranging from simple pyrrolidine derivatives to tropane esters derived from angelic, tiglic, senecioic or methylmesaconic acids were obtained from in vitro regenerated plantlets. One of thern, 3 alpha-methylmesaconyloxytropane was not previously described. The same growth conditions, as well as other growth regulator levels tested, were required to induce callus and root formation in S. grahamii Gill. Root organogenesis occurred despite a high level of BA vs. NAA used, (i.e., 4.44 mu M BA and 0.54 mu M NAA); however no shoot formation was achieved. In the case of S. tricolor Grau et Gronbach, only callus formation was obtained in the presence of various growth regulators.